2. A Guide to Unix Using Linux
Fourth Edition
Chapter 1
The Essence of UNIX and Linux
3. Objectives
• Explain operating systems, including PC and server
operating systems
• Describe the UNIX and Linux operating systems
• Explain the purpose of UNIX/Linux shells
• Understand how to select user names and
passwords
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5. PC Operating Systems
• A personal computer system, or PC, is usually a
stand-alone machine
– E.g., desktop or laptop computer
• A PC OS conducts all the input, output, processing,
and storage operations on a single computer
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6. Server Operating Systems and
Networks
• A computer network lets PCs share resources
• A server OS controls the operations of a server or
host, which accepts requests from clients
• Peer-to peer networks are an alternative to
server-based networks
– Each system on the network is both a server and
client
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8. Introducing the UNIX and Linux
Operating Systems
• UNIX/Linux is used on systems functioning as:
– Servers, clients, client/server workstations, and
stand-alone workstations
• UNIX/Linux are multiuser/multitasking systems
• Some characteristics of UNIX/Linux systems:
–
–
–
–
–
Portability
Stable, reliable, and versatile
Thousands of applications are written for them
Many security options
Well suited for networked environments
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9. A Brief History of UNIX
• Originally developed at AT&T Bell Labs
– Late 1960s and early 1970s
– Distributed in source code form
• Two standard versions evolved:
– AT&T Bell Labs produced SystemV (SysV)
– UC Berkeley developed BSD
• Linux might be considered a more integrated
version of UNIX than its predecessors
• POSIX: effort of experts from industry, academia,
and government to standardize UNIX
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11. Linux and UNIX
• Linux is a UNIX-like operating system
– Not written from the traditional UNIX code
– Kernel created to look and act like UNIX
• Enhancements include the POSIX standards
• Linus Torvalds released it free of charge in 1991
– Many distributions are available:
•
•
•
•
•
Debian GNU/Linux
Fedora
Red Hat Enterprise Linux
openSUSE Linux
Ubuntu
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12. Introducing UNIX/Linux Shells
• Shell: program that interprets commands you enter
from keyboard
– Bourne shell, developed by S. Bourne (AT&T Bell
Labs), was the first UNIX command processor
– Another Bell employee developed the Korn shell
• History feature
– C shell is designed for C programmers’ use
– Linux uses Bash shell as its default shell
• Graphical user interface (GUI) desktop can open
a terminal window
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13. Choosing your Shell
• Shells do much more than interpret commands
– Extensive built-in commands turn shells into firstclass programming languages
• A default shell is associated with your account
when it is created
– You may switch to another shell after you log in
• Many users prefer the Bash shell
• Other shells:
– Bourne, ksh, csh, ash, tcsh, zsh
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14. Switching from Shell to Shell
• Switch to another shell by typing the shell’s name
on the command line
– For example, type tcsh, bash, or ash
– Work in that shell until you:
• Log in again
• Type another shell name on the command line
• Users often use one shell for writing shell scripts
and another for interacting with a program
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15. User Names and Passwords
• User Name vs. Key Word
• Special Characters
• Consideration for Console Operations
• Security
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